The present invention relates to an electronic control apparatus for effecting control of an internal combustion engine mounted on an automobile or various other kinds of controls such as height control or brake control on the automobile.
In general, a typical electronic control apparatus for use in an automobile is disposed in a driver's or passenger's compartment and is connected by a considerably long wire harness to sensors, actuators or the like which are mounted in an engine compartment and on an internal combustion engine.
For this reason, external noise which may enter the wire harness has been a problem.
To solve the problem, such an electronic control apparatus may be provided in the engine compartment so that the wire harness can be made as short as possible.
However, if the electronic control apparatus is provided in the engine compartment, the temperature in the engine compartment raises a serious problem. More specifically, the air temperature in the engine compartment can be maintained at a considerably low temperature when an automobile is running since fresh air flows into the engine compartment. However, when the automobile is stopped after its high-speed running, air stagnates in the engine compartment and heated by the heat of the internal combustion engine, with the result that the air temperature in the engine compartment rises to a high level.
If the electronic control apparatus for an automobile is exposed to such a high temperature for a long time, then a problem occurs that semiconductor devices which constitute a part of the electronic control apparatus cannot maintain their normal functions.
For this reason, it is necessary to cool the electronic control apparatus for an automobile. As a cooling method, Japanese Patent Unexamined Publication No. 50-58987 proposes a method of cooling an electronic control apparatus for an automobile by using gasoline supplied to an internal combustion engine.
However, when gasoline is used as a cooling medium as described above, the following problems will be encountered:
(1) Since gasoline is introduced into the electronic control apparatus for an automobile, it is necessary to design a special sealed structure for anti-leak purposes. If a leakage of gasoline should occur, the possibility of fire is extremely high;
(2) Since gasoline is intended to absorb the heat generated in the electronic control apparatus for an automobile, the temperature of gasoline rises, so that vapor bubbles are easily produced, with the result that a vapor lock may occur in fuel injection valves.